In a solid state image sensor having a pixel array, a first frame is imaged using varying exposure times in a series of zones. The exposure time for a subsequent frame is selected from the results of the first frame, The exposure times are controlled in a rolling blade manner by controlling the number of lines between reset and readout. The sensor is particularly suited to use in bar code readers.
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1. A method of setting an exposure time in a solid state image sensing system comprising an array of pixels, a reset unit for resetting the pixels, and a readout unit for reading out pixel values, the method comprising: controlling the reset and readout units for exposing a first image frame as a series of frame zones to generate a series of respective zone signals, each frame zone comprising successive groups of rows of pixels and being exposed for a different exposure time, with each frame zone having a progressively increasing exposure time, determining a best exposure time based upon the series of zone signals, and with the best exposure time including interpolation between zone exposure times of the first image frame, and exposing a second image frame as a whole frame using the best exposure time.
In a machine vision system with a pixel array, this method sets the exposure time. First, it captures an initial image frame divided into multiple horizontal zones. Each zone consists of pixel rows and is exposed for a different, progressively increasing time. The system reads out signals from each zone. Then, it analyzes the zone signals to determine the best exposure time for the scene, even interpolating between the zone exposure times. Finally, it captures a second, full-frame image using this best-calculated exposure time.
2. The method according to claim 1 , wherein the respective exposure times for the zones are set using a rolling blade process with different time delays between reset and readout.
This exposure time setting method, like the one where an initial image frame is captured as a series of zones with different exposure times to determine the best exposure, uses a "rolling blade" technique to control the exposure time of each zone. The rolling blade involves varying the time delay between resetting the pixels and reading out their values, creating different exposure times for each zone.
3. The method according to claim 1 , wherein determining a best exposure time further comprises processing the zone signal from each zone to generate a statistical value of an image sensed in the respective zone.
This exposure time setting method, like the one where an initial image frame is captured as a series of zones with different exposure times to determine the best exposure, determines the best exposure time by processing the signal from each zone to generate a statistical value. This statistical value represents an image characteristic sensed in that particular zone, which is then used to optimize the exposure setting for the full image.
4. The method according to claim 3 , wherein the image sensing system includes an image sensor on a chip; and wherein the processing is carried out on the same chip as the image sensor.
In this exposure time setting method, which processes zone signals to generate statistical values for determining the best exposure, the image sensing system, including the image sensor, is integrated onto a single chip. The statistical processing of the zone signals is also carried out on the same chip as the image sensor, enabling faster and more efficient exposure control.
5. The method according to claim 1 , wherein exposing the first image frame comprises sensing a digital pattern image.
In this exposure time setting method, like the one where an initial image frame is captured as a series of zones with different exposure times to determine the best exposure, the initial image frame that's captured for exposure analysis contains a digital pattern. Instead of a normal scene, the camera looks at a controlled pattern to determine optimal exposure.
6. The method according to claim 5 , wherein the digital pattern image comprises a bar code.
In this exposure time setting method, which involves sensing a digital pattern image for exposure setting, the digital pattern is a bar code. The system analyzes the barcode image captured with varying exposure zones to determine the best exposure level for accurately reading the barcode in a subsequent full-frame capture.
7. A method of setting an exposure level in an image sensing system comprising an array of pixels, a reset unit for resetting the pixels, and a readout unit for reading out pixel values, the method comprising: controlling the reset and readout units for exposing a first image frame as a plurality of frame zones to generate a series of readout values, each frame zone comprising successive groups of rows of pixels and being exposed for a different exposure level, with each frame zone having a progressively increasing exposure level, selecting an image exposure level based upon the series of readout values, and with the exposure level including interpolation between zone exposure levels of the first image frame, and exposing a second image frame using the selected exposure level.
This method dynamically adjusts the exposure level in an image sensor. It captures an initial frame divided into horizontal zones, each with a different, progressively increasing exposure level. The system reads out values from each zone. Based on these readout values, the system selects an optimal exposure level, potentially interpolating between zone exposure levels. A second, full frame image is then captured using the selected exposure level.
8. The method according to claim 7 , wherein the respective exposure levels for the zones are set using a rolling blade process with different time delays between reset and readout.
This exposure level setting method, like the one where an initial image frame is captured as a series of zones with different exposure levels to determine the best exposure, uses a "rolling blade" process to set different exposure levels for the zones. The rolling blade controls exposure by adjusting the time delay between pixel reset and readout for each zone.
9. The method according to claim 7 , wherein selecting the image exposure level further comprises processing the readout values from each zone to generate a statistical value of an image sensed in the respective zone.
In this method for setting exposure level, like the one where an initial image frame is captured as a series of zones with different exposure levels to determine the best exposure, the image exposure level is selected by processing the readout values from each zone to generate a statistical value. This statistical value is used as a metric to assess the image quality in each zone and select the best overall exposure.
10. The method according to claim 7 , wherein exposing the first image frame comprises sensing a digital pattern image.
This exposure level setting method, like the one where an initial image frame is captured as a series of zones with different exposure levels to determine the best exposure, the initial image frame is designed to sense a digital pattern image. Instead of a normal scene, the camera looks at a controlled pattern to determine optimal exposure.
11. The method according to claim 10 , wherein the digital pattern image comprises a bar code.
In this exposure level setting method, where the initial image frame comprises sensing a digital pattern image, the digital pattern is a bar code. The image sensor captures and analyzes the barcode image using different exposure levels to determine the optimal exposure for reliably reading the barcode.
12. An image sensing device comprising: an array of pixels; a reset unit for resetting the pixels; a readout unit for reading out pixel values; and a control unit for controlling the reset unit and readout unit to expose a first image frame as a series of frame zones to generate a series of respective zone signals, each frame zone comprising successive groups of rows of pixels being exposed for a different exposure time, with each frame zone having a progressively increasing exposure time, determine a best exposure time based upon the series of zone signals, and with the best exposure time including interpolation between zone exposure times of the first image frame, and expose a second image frame as a whole frame using the best exposure time.
An image sensing device has a pixel array, reset, and readout units. A control unit divides an initial image capture into a series of horizontal zones, each exposed with a different, progressively increasing exposure time. The system measures a readout from each zone. Based on the zone readouts, it determines an optimal exposure time, potentially interpolating between zone exposure times. The device then captures a full image using this optimal exposure.
13. The image sensing device according to claim 12 further comprising a processing unit to produce zone statistics from the readout pixel values of each frame zone.
This image sensing device, like the one where an initial image frame is captured as a series of zones with different exposure times to determine the best exposure, also contains a processing unit. This processing unit takes the readout pixel values from each frame zone and calculates zone statistics. These statistics provide information about the image quality in each zone to optimize exposure settings.
14. The image sensing device according to claim 12 wherein the device is for sensing a digital pattern image; and further comprising a lens system for forming an image of the digital pattern image on the pixel array.
This image sensing device, like the one where an initial image frame is captured as a series of zones with different exposure times to determine the best exposure, is designed to sense a digital pattern image. It includes a lens system that focuses the image of the digital pattern onto the pixel array. The device then analyzes the captured image to optimize exposure settings.
15. The image sensing device according to claim 14 wherein the device is a handheld mobile device for reading bar codes.
This image sensing device, like the one where an initial image frame is captured as a series of zones with different exposure times to determine the best exposure, which is also designed to sense a digital pattern image and includes a lens system for capturing the image, is a handheld mobile device specifically for reading barcodes.
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November 13, 2006
July 2, 2013
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